The season’s first Nor’wester, followed by rain, lashed the city on Wednesday afternoon, forcing people to scamper for cover.

Deputy director-general of the regional meteorological centre at Alipore, R.N. Goldar, said the storm was severe in north Calcutta, while south Calcutta remained relatively calm.

“In Dum Dum, the Nor’wester struck twice, the first time around 2.30 pm at 74 kph and the second at 82 kph,” he added.

The squall brought down temperatures in the northern part of the city by around six degrees. Dum Dum and other areas in north Calcutta and its suburbs received 50 mm of rain, but Alipore recorded only 1.5 mm.

The Met office, however, allayed fears of Holi revellers — the Festival of Colours is just six days away — that the weather was likely to clear within the next two days.

“We can expect rain, accompanied by strong winds, during the next 24 hours. The weather, however, is likely to clear within 48 hours,” Goldar said.

A trough of low pressure over Chhattisgarh, Jharkhand and north Orissa, along with an upper-air circulation, triggered the Nor’wester and the showers, the Met office said.

Loath to take chances, the city civic authorities alerted the pumping stations in the afternoon to gear up for heavy rain.

Air Sahara’s Guwahati flight returned to Calcutta because of inclement weather. Flights to Delhi and Mumbai were delayed.